背景 前列腺（或稱攝護腺）位於膀胱與尿道之間，居於前列腺腺體中央之尿道，於排尿功能扮演重要角色。當前列腺之腺體體積增加時，將擠壓前列腺尿道，造成排尿困難的現象。根據文獻報告，尿道之尿流控制區域之延展性，於決定尿流之性質，扮演重要角色；於一般男性，尿流控制區域位於外括約肌位置；但於前列腺增生（肥大）之患者，則位於前列腺尿道區域。不過，於前列腺尿道之材料性質，相關之報告，則不多。本研究之目的，建立可靠之量測方法，量測前列腺尿道之生物力學性質；更進一步，施行於前列腺尿道周邊之性質評估。

材料與方法 共9個人類前列腺檢體，來自於前列腺癌或膀胱癌患者，施行前列腺根除手術及膀胱前列腺根除手術。應力與應變檢測，於獲得檢體之72 小時之內完成。量測器材包括：MTS TytronTM microforce testing system，5磅load cell，一支14公分長 斜角3.8度之錐狀金屬棒 及資料蒐集系統。應力與應變之量測時，錐狀金屬棒前進方向，由近端即膀胱端往遠端即尿道出口端推，錐狀金屬棒口徑由小至大。應力之收集由最小至MTS Tytron前進之最大範圍。共7個檢體完成量測，及5組資料完成分析。

結果 本研究之彈性系數（Elastic modules，E ）之公式推導。 E=F/2π (ε1 sinθ/(2γ0))) (F: radial force, : 厚度, θ:3.8度, :前列腺腺體長度 (公分), ε1: (γ1/γ0)-1, γ0: 金屬棒之初半徑) 初始位置之直徑從6.208 公釐至8.296公釐；直接測量到之直徑為4.04至10.40公釐。本研究顯示，在循環性的負荷過程，應力與應變之關係，發生改變。在形變量小於百分之八十內，楊氏係數與應力之改變屬於線性變化；而且改變量不大。儘管形變量增加百分之百，楊氏係數小於0.053 (N/m2) 應力小於0.167 (Pa)。

結論 尿道周圍之組織符合黏彈體之特性。依本離體實驗發現，人類前列腺之尿道周圍組織俱有高度彈性，對尿道之阻力影響不大。因此，打開前列腺尿道之所需之力量並不大。

Introduction Prostate gland, surrounding the proximal urethral lumen, plays an important role in urination function. As the mass of prostate gland increased, it will compress urethral lumen and result in voiding with difficulty. The distensibility of the flow-controlling zone (FCZ) in the urethra is considered to be the major factor determining urethral flow properties. However, the reports of the biomechanical properties on prostate gland are limited. The aims of this study are to establish a reliable technique to measure the biomechanical properties on prostate gland and further, to investigate the elasticity of periurethral tissue in the prostate.

Materials and Methods A total of 9 human isolated prostate glands are collected from radical surgery for prostate cancer or bladder cancer. After obtaining the specimens, the measurement of elasticity and stress is completed within 72 hours. MTS TytronTM microforce testing system with a 5-lb load cell and a 14-cm tapered metal rod with 3.8o in slope is used to measure the force detected by the data acquisition system. The force is measured between minimal and maximal resistance by passing the tapered metal rod through prostate urethra in normal urination direction. A total of 7 cases completed the study and 5 cases finished the data analysis.

Results This study demonstrated the stress-strain relationship in the loading process is different from that of the previous status under cyclic loading. Elastic modules (E) is calculated using formula: E=F/2π (ε1 sinθ/(2γ0))) (where F: radial force, : thickness, θ:3.8o, : prostate length (cm), ε1: (γ1/γ0)-1, γ0: initial radius of tapered metal rod) The diameters at the (γ0) position ranged from 6.208 mm to 8.296 mm and the urethral diameters measured from 4.04 mm to 10.40 mm. Within the strain less than 0.8, the relationships between strain and Young’s moduli , and stress are in the linear part. Although the strain increased 100%, the Young’s moduli are less than 0.053 (N/m2) and stress are less than 0.167 (Pa).

Conclusions Periurethral tissue in the prostate gland is compatible with viscoelastic characteristics. This ex vivo study suggested that periurethral tissues in the human prostate gland are highly elastic and do not play major contribution in urethral resistance. It also suggested that to open the prostate urethra does not need strong driving force.

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